Adapter for a printed circuit board testing apparatus

ABSTRACT

An adapter (175) for a printed circuit board testing apparatus. The adapter serves to connect testing contacts located in the grid to testing points, located in and/or out of grid, of a printed circuit board to be tested, through adapter pins (181). The adapter pins (181) are conically tapered at their ends facing the testing points. The adapter (175) has a first guide plate (176), a second guide plate (177) and a third guide plate (178) lying in between. The first guide plate (176) only has holes (180) only located in the grid. The second guide plate (177) has holes (179) located in the grid, as well as holes (179a) located out of grid. In order to guarantee that the testing pins (181), with perpendicular introduction into the guide holes (180) of the first guide plate (176), are inevitably always guided into the corresponding guide holes (179, 179a) of the second guide plate (177), the displacement for holes, located out of grid, in the third guide plate (178) is so chosen n that the conical points of the adapter pins (181) in any case still go home into the corresponding guide hole (182a), located out of grid, of the third guide plate (178).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an adapter for a printed circuit board testingapparatus and more particularly to an adapter which has testing contactslocated in a grid and which can be connected through adapter pins totesting points located in and/or out of the grid, of a printed circuitto be tested.

2. Description of the Related Art

Adapters of the type to which this invention relates have a first and asecond guide plate, which are arranged parallel to one another and at adistance from one another and have guide holes for the adapter pins,into which the adapter pins can be plugged, in which case the guideholes in the first guide plate are arranged in the grid and in thesecond guide plate in the pattern of the testing points of the printedcircuit to be tested.

An adapter of this type is the subject matter of a prior proposal of theapplicant, which comprises the fitting-out of such an adapter both formachine assembly as well as for manual assembly of the adapter. With theembodiment for machine assembly a particular orientation device for theadapter pins is allocated to the adapter, which limits their excursionmovements on the introduction of the adapter pins into the guide holes.With the embodiment for manual assembly the adapter is allocated anoptically acting additional device, through which the introduction ofthe adapter pins is made easier.

For adapters of the present type, the requirement exists that, to avoidshort circuits, the adapter pins must not touch each other. With thegiven grid dimensions and necesssary dimensions for the adapter pins,for the guide hole diameter and for the thickness of the guide plates,as well as the distance between the same, the above requirement is noteasy to fulfill. As well, it must be taken into account that the adapterpins should be as easy as possible to introduce.

SUMMARY OF THE INVENTION

The underlying object of the invention is to design an adapter of theabove described construction at the start, so that mutual contact ofadapter pins does not occur and easy running of the adapter pins isguaranteed.

The present invention in one aspect is characterized in that the firstguide plate has guide holes at all grid points, and the distance betweenthe first and second guide plates is alterable between a workingposition, in which the guide plates have a separation shorter than thelength of the adapter pins, and an assembly position, in which the guideplates have a separation from another which is reduced compared with theworking position. Further, the separation in the assembly position issuch that an adapter pin to be introduced into a guide hole of thesecond plate can, as a result of a maximum angle of deviation of the pindefined by the pin diameter as well as the diameter and length of theguide holes of the first guide plate, be introduced through one of atmost four guide holes arranged next to one another in a square in thefirst guide plate.

With the design according to the invention, through the particularlimiting of the angle of deviation of the pin, care is taken that anadapter pin in such a position in which it could touch another adapterpin, cannot be plugged in at all. In order to cause the contact of oneadapter pin with another adapter pin, namely one of these two adapterpins would have to be plugged-in into a guide hole of the second guideplate, which is displaced to the allocated grid point by a greateramount than is given through the maximum angle of deviation of the pin.Thus the relevant adapter pin cannot be introduced into such a guidehole.

A further advantage of the distance alteration according to theinvention can be seen in the fact that the angles of deviation of thepins actually present diminish when the distance between the guideplates increases. This leads to an increase of the movement clearance ofthe adapter pins in the guide holes and is in particular of significancefor the guide holes in the second guide plate, which are displaced tothe allocated grid point by the maximum extent given through the designaccording to the invention, and into which the relevant adapter pins ineach case can just still be introduced with difficulty. According to thedistance increase, which results when moving one or both guide platesinto the working position, the adapter pins plugging in these maximallydisplaced guide holes of the second guide plate are also easy-running,which is required for function reasons.

The design according to the invention can likewise be advantageouslyused both for machine assembly as well as for manual assembly of anadapter with adapter pins.

Through the design according to the invention, moreover, the adapter isconsiderably simplified and the introduction of the adapter pins madeeasier than in prior art arrangements. The simplification consists inthat, the first guide plate has guide holes at all grid points and is,therefore, the same for all adapters.

By providing a transparent style of the first guide plate, theintroduction of the adapter pins with hand assembly is made easier,because the operator is able to recognise optically the guide holes inthe second guide plate, into which the adapter pins must be plugged-in.By reason of the pellucid, namely transparent, or almost transparentstyle character of the first guide plate, the guide holes in the secondguide plate are clearly visible. The visibility is improved by the factthat, in the assembly position the guide plates have a relatively smalldistance from one another, which must be matched with the dimensionvariables according to the invention.

By providing a particular guide between the first and the second guideplates for adjusting one or the other, the distance alteration can beeasily realised. As well, the first guide plate or the second guideplate or also both guide plates can be simultaneously adjusted.

A distance alteration between the guide plates can also be made easierthrough the allocation of an adjusting mechanism. Such a mechanism ispreferred, which fixes the relevant guide plate or the guide plates inthe end positions. Spindle drives or cylinder-piston drives may be usedas adjusting drives.

The present invention in another aspect is characterized in that thefirst guide plate has guide holes only at the grid points to whichtesting contacts are allocated at the printed circuit board and in thata third guide plate which extends between the first and second guideplates likewise only has holes at such grid points to which testingcontacts are allocated at the printed circuit board. Further, the guideholes lying out of grid of the third plate are displaced less far,compared with corresponding grid points that the corresponding guideholes lying out of grid, of the second guide plate. The holes in thethird guide plate lie in guide alignment between mutually allocatedholes in the first and second guide plates.

With this design according to the invention, a mutual contact of adapterpins is avoided through the fact that each required adapter pin isallocated a forced guide, which results in only one plug-in possibilityfor each adapter pin, i.e. the adapter is 100% reproducible.

This is guaranteed by the fact that every adapter pin plugged into aguide hole of the first guide plate, can only be plugged into a guidehole in the third guide plate which is allocated to a correspondingguide hole in the first guide plate, and which is located in guidealignment with the guide holes, allocated to one another, in the firstguide plate and in the second guide plate.

The movement clearance of the relevant adapter pin in the guide hole ofthe first guide plate and the distance between the first guide plate andthe third guide plate, as well as the size of the allocated guide holein the third guide plate are matched to one another so that, the plug-inend of the adapter pin dips inside the hole edge of the guide hole inthe third guide plate into the latter and into the allocated guide holein the second guide plate. Of advantage are adapter pins which arepointed at their plug-in ends, in which case the arrangement is so metthat the pin points lie, with maximum angles of deviation of the pins,within the hole edges of the guide holes in the third and in the secondguide plate.

A further advantage of this design according to the invention consistsin that, the adapter can be particularly easily filled. Moreover, guideholes must only be bored into the first guide plate in a number whichcorresponds to the number of testing points on the printed circuitboard, i.e. to the number of guide holes in the second guide plate.

With this aspect of the invention, the first guide plate does not needto consist of clear material e.g. plexiglass. It can consistadvantageously of a synthetic material made from an epoxy resin, inparticular one strengthened by glass fibres, which is considerablyeasier to bore than, e.g. plexiglass. The strengthening inset in thethird guide plate is, therefore of significance, because it reduces withlarge guide plates the sagging of the guide plates.

The extent of the displacement, with which a guide hole in the thirdguide plate is displaced compared with the grid point allocated to it,is defined through the relationship of the distances between the firstguide plate and the third guide plate and the distance between the thirdguide plate and the second guide plate. The angle of deviation of thepin results from the guide clearance of the adapter pin in the firstguide plate, in which case the pin diameter, the guide hole diameter andthe guide hole length have influence.

A large angle of deviation of the pin results inevitably in a largepivoting circle in the region of the third guide plate. In a preferredarrangement of the invention the distance between the second and thirdguide plates amounts to about 80% of the distance between the first andsecond guide plates. This is advantageous, because by reason of thenecessary movement clearance of the adapter pin in the first guideplate, the excursion circle which can be described by the introductionend of the adapter pin is relatively small, so that with relativelysmall movement clearance in the guide hole in the third guide plate,blockages when introducing the adapter pin through the free adapter pinend striking on the hole edge of the guide hole in the third guide plateare avoided and, by reason of the relatively small movement clearance inthe third guide plate, a striking on the hole edge of the guide hole inthe second guide plate is likewise avoided. If the third guide platewere located directly underneath the first guide plate, then an enlargedpivoting circle of the introduction end of the adapter pin would resultin the region of the second guide plate. A balanced relationship of thedistances of the third guide plate from the first guide plate and thesecond guide plate is then given, if the distance between the secondguide plate and the third guide plate amounts to about 80% of thedistance between the first guide plate and the second guide plate.

By providing a translucent lower guide plate, the introduction of theadapter pins can be observed from below by reason of the translucency.This is possible, because the end, of the relevant adapter pin, to beintroduced can be recognised either directly or as a silhouette. As aresult of this, the adapter pin can be introduced controllably andtherefore can be directed according to specific objectives into theguide hole allocated to it.

Furthermore, a transparent lower guide plate is not definitely needed,but rather it also suffices if the lower guide plate is translucent tosuch an extent that, the adapter pin point to be introduced throws ashadow on it, which can be recognised through the lower guide plate.Hereto a light source is naturally required, which is arranged above thelower guide plate.

The light does not have to be arranged above the adapter pin, for asideways light source also throws a shadow of the relevant adapter pinonto the lower guide plate, which proceeds from the adapter pin point.

By providing a mirror below the lower guide plate, the control withregard to the viewing position is simplified.

In a preferred arrangement, a central guide plate is arranged betweenlower and upper guide plates which have guide holes provided in all gridpoints and which have a diameter which allows limited steering clearanceof the adapter pins. With this arrangement, the adapter pins are given,by reason of the enlarged guide holes in the central guide plate, alimited clearance space on all sides, which makes it possible, to steerthe adapter pins to and fro, in which case the largest amount ofdeviation can be pre-determined through the size of the guide holes inthis guide plate. Through a suitable size dimensioning of these guideholes the movement clearance space of the adapter pins can be limited tothe guide holes lying closest to the adapter pin points to beintroduced. Through this limiting, the introduction of the relevantadapter pin point into a guide hole lying farther away is prevented.

By providing a lamp above the upper guide plate and by making thecentral and/or the upper guide plate translucent, it becomes possible,as already mentioned, to arrange the light source so far above the lowerguide plate that the light spreads out somewhat axially to the adapterpins and throws below the adapter pin points small clear shadows ontothe lower guide plate. With corresponding selection of the translucencyor transparency of the upper plate and of the central guide plate itbecomes possible to exploit a usual space lighting from the spaceceiling for the shadow formation, according to the invention, on thelower guide plate.

By arranging the central guide plate to move perpendicularly to thelower and upper guide plates, it is possible, to alter the previouslymentioned clearance space, on all sides, for the adapter pins, forexample according to the present grid size. This becomes possiblethrough a moving of the central guide plate. The further the centralguide plate is pushed towards the upper guide plate, the greater thistapering clearance space becomes, in which the adapter pins can besteered to and fro. Should this clearance space be limited, then thecentral guide plate must be moved in the direction of the lower guideplate, that is, distanced from the upper guide plate.

Since, with an adapter of the present construction type the adapter pinstake on different inclinations, the requirement exists for a headdevelopment for the adapter pins, which makes possible a close set inthe region of the hole edges of the upper guide plate. This requirementis fulfilled, according to a preferred form of the invention byproviding adapter pins with spherical heads. By reason of the sphericaldevelopment of the heads, they always lie fully at the respective holeedge, namely independently of the inclined state of the relevant adapterpin.

According to a further preferred form of the invention a hand lamp isarranged above the upper guide plate. This provides aposition-independent lighting which makes it possible to carry out thelighting directed at specific objectives, so that the soughtsilhouetting on the lower guide plate can be optimally produced.

Since the adapter is a component which is complete in itself, it isrecommendable to fasten the mirror to a holder, on which the adapter canbe set for the purpose of assembling the adapter pins.

If the mirror is inclined compared with the lower guide plate to thefront or rear side of the adapter, the mirror image can be read moreeasily, through a mirror device comprising two mirrors, e.g. into theeye height of the operator.

According to a further aspect of this invention there is provided anovel adapter for a printed circuit board testing apparatus, by means ofwhich testing contacts located in the grid can be connected to testingpoints located in and/or out of the grid of a printed circuit board tobe tested. In this aspect of the invention adapter pins are providedwhose ends turned toward the testing points taper conically, with finaland second guide plates, and a third guide plate lying between the firstand second plates, all three of which are arranged parallel and at fixeddistances to one another and all three of which have guide holes for theadapter pins, with the guide holes of the first plate located in thegrid and the guide holes of the second plate located in and/or out ofthe grid and coinciding with the testing points of the printed circuitboard to be tested. The third plate likewise has guide holes located inand/or out of grid.

This aspect of the invention is characterized in that the holes locatedout of grid, of the third guide plate, are so placed that the adapterpins on the one hand with perpendicular introduction into the guideholes of the first guide plate in any case still enter, with theirconically tapering end, into these guide holes located out of grid, andon the other hand, are, with further introduction, are steered throughthese guide holes, located out of grid, of the third guide plate,coercively into the out of grid guide holes of the second guide plate.This aspect of the invention makes it possible to dimension individualparts of the adapter so that a simple loading in a short time isguaranteed, in which case the loading efficiency should be as near to100% as possible. That means that post-loading of individual holes byhand can be eliminated. The adapter should be suitable in particular forloading with an automatic loading system, as is described in DE-OS No.33 40 184 of the applicant.

According to a still further aspect of the invention there is provided anovel method for indicating locations of errors on a printed circuitboard to be tested with testing points located in the and/or out ofgrid, employing an adapter as above described. This method should makepossible a particularly simple direct indication of the error sources ora simple seeking of the locations of errors on the printed circuit boardaffected by errors. This aspect of the invention is characterized by thesteps of supplying to a computer, data representing the co-ordinates ofall contact holes of a printed circuit board to be tested, causing thecomputer to calculate and indicate the co-ordinates of the bore holesfor the three adapter guide plates, boring the holes in the three guideplates corresponding to the calculated coordinates, thereafterassembling the adapter from the guide plates, introducing the adapterpins, supplying the adapter with the printed circuit board to be testedto a printed circuit board testing apparatus, causing the testingapparatus to transmit to the computer the data or co-ordinates of thosetesting contacts located in the grid, which correspond to testing pointsaffected by errors located in and/or out of grid of the printed circuitboard, causing the computer, by reason of these data or co-ordinates, todetermine the data or coordinates of the testing points located inand/or out of grid and to cause an indicating apparatus to indicatethese data or co-ordinates in a manner such that the testing pointsaffected by error may be sought out on the printed circuit board to betested or marked by means of an error indicating device.

It is a significant point of the mentioned method, that a computer usedfor calculating the bore diagram for the guide plates of the adaptor canbe exploited in addition to convert the data or co-ordinates of thetesting contacts determined by the printed circuit board testingapparatus, which correspond to testing points affected by errors,located in the and/or out of grid, of the printed circuit board to betested, into the data or co-ordinates of the last-named testing points,so that they can either be sought on the printed circuit board ordirectly marked optically. This conversion is required, because theprinted circuit board testing apparatus can only fix the data orco-ordinates of the mentioned testing contacts, which lie on the side ofthe first guide plate of the adapter, that is in the grid. Desired are,however, the data or co-ordinates of the testing points, affected byerrors, on the printed circuit board, lying partially out of grid, whichare located on the side of the second guide plate of the adapter. Sincethe computer knows both the data or co-ordinates of the guide holes ofthe first guide plate, as well as those of the second guide plate, theconversion is possible without difficulties.

It is possible to indicate the data or co-ordinates of the testingpoints, affected by errors, of the printed circuits boards to be testedon a monitor and then to seek the testing points affected by errors bymeans of an optical search system. This optical search system can forexample function like a usual drafting machine, with which bothco-ordinates of the respective position of the signal head areindicated. The signal head equipped in this case with a magnifying glasssystem with cross wires can then be driven into that position, whichcorresponds to the determined co-ordinates.

It is, however, also possible to mark the locations of errors on theprinted circuit board to be tested directly, for example through a lightpoint, in which case the light point is thrown onto the printed circuitboard by a projector which can be driven in two co-ordinate directions.To the control of the projector the data or co-ordinates determined bythe computer are then supplied.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following several embodiments of the invention are describedsupported by a simplified drawing. There is shown in:

FIG. 1 a partial section through an apparatus for testing printedcircuit boards, in which case the partial section runs perpendicular tothe adapter, designed according to the invention, received in theapparatus;

FIG. 2 a perpendicular section through an adapter located on an assemblyholder as first embodiment;

FIG. 3 a partial section along the line III-III in FIG. 2;

FIG. 4 a further development of the adapter according to FIG. 2;

FIG. 5 a perpendicular section through an adapter in another embodiment;

FIG. 6 a cutout of the adapter according to FIG. 5 in plan view;

FIG. 7 the adapter according to FIG. 5 in its working position;

FIG. 8 a perpendicular section through an adapter in a furtherembodiment;

FIG. 9 a schematic sectional view of an adapter consisting of threeguide plates with particular dimensioning of the guide holes of thethird guide plate and;

FIG. 10 a graphic portrayal, which shows the course of a method forfixing and indicating location of errors on a printed circuit board tobe tested.

In FIG. 1 a receiving plate of the apparatus, not shown completely, fortesting printed circuit boards, is designated by 1. On this receivingplate 1 a printed circuit board 2 with testing points 3 is located.Above the printed circuit board 2 to be tested are located a grid holeplate 4, whose holes 5 are arranged in the grid and two modules 6,movable in the direction of the printed circuit board 2 and back, whichare provided on their lower fore parts with testing contacts 7 in theform of pins, which, in the driven away position of a module 6, extendthrough the holes 5 in the grid hole plate 4. The testing contacts 7carry telescopic testing contact heads 8 which can be driven in and out,which are pre-stressed in the direction of their outer end position by aspring which is not portrayed.

The testing contacts 7 are fastened in the modules 6 by encapsulationand stand are connected by electric lines 9 with printed circuit boards12, carrying IC-chips 11, which are arranged inside the modules 6 andform, in their unity with the printed circuit boards 12 the IC-chips 11and if necessary further components, a partial circuit matrix allocatedto the testing contacts 7.

On the printed circuit board 2 a grid adaptation adapter 13 is located,which has a multitude of adapter pins 14 extending through it, whichlink the testing contacts 7 arranged in the grid with the testing points3 arranged out of grid. The adapter pins 14 do not lie, therefore, inthe respective alignment with the testing contacts, but rather extendaslant through the adapter 13, in which case they project with both endsout of the adapter and form contact places which are raised comparedwith the upper and lower side.

From FIG. 2 the construction of the adapter 13 can be seen. The adapter13 consists of a lower guide plate 15 with guide holes 16 arranged inthe pattern of the testing points of the printed circuit board 2 to betested which is not portrayed in FIG. 2, and an upper guide plate 17extending parallel to it at a distance above, with guide holes 18 forthe adapter pins 14 arranged in the grid. The guide plate 15 and theguide plate 17 form, with fore plates 19 fastened to them on the foreside, a box shape.

The adapter pins 14 can be introduced from above through the guide holes16, 18 and they have at their upper ends spherical heads 21, which restin the fully introduced position against the edges 22 of the guide holes18. Five adapter pins 23 to 27 are portrayed, of which the adapter pins23 to 25 are fully introduced, whilst the adapter pins 26 and 27 standup on the guide plate 15. Whilst the guide holes 16, 18 for the adapterpins 23 and 26 are flush with one another, that is lying in the grid,the guide holes 16, 18 for the adapter pins 24, 25 and 27 are not flushwith one another, because these guide holes in the guide plate 15 arelocated out of grid, whereby an aslant position of the fully introducedadapter pins 24, 25 and 27 is called for.

The adapter 13 is located on an assembly holder 31 for the purpose ofthe introduction of the adapter pins 23 to 27, which are introduced byhand. Below the guide plate 15, in the assembly holder 31, a mirror 32is fastened, which is inclined to the front side of the adapter 13, i.e.to the side on which the operator stands. A handlamp portrayed by way ofa suggestion and designated by 33 is located above the guide plate 17and is held for example in one hand by the operator. The guide plate 17consists of a synthetic material, which is not transparent, yet letsthrough a definite amount of light, so that the guide plate 15 is alsostill lit by the light rays of the hand lamp 33. Since the guide plate15 likewise consists of a material which is slightly translucent, theshadow thrown onto the guide plate 15 by the adapter pins 26, 27 isvisible from below. Therefore, not only the guide holes 16 of the guideplate 15, but also the shadows designated by 34 are outlined on themirror 32. The operator can, by reason of this shadow illustration,recognise on which side of the relevant guide hole 16 the relevantadapter pin points are located. Through corresponding steering movementsof the adapter pins 26, 27, which are brought about through manualcontact on the spherical heads 21, the adapter pin points can beintroduced, directed to fixed objectives, into the appertaining guideholes 16.

With the exemplary embodiment according to FIG. 2 the amount ofdeviation designated by a is defined through the diameter d of the guideholes 18, through which the adapter pins 14 extend, with a certainmovement clearance.

With the second exemplary embodiment according to FIG. 4, between theguide plate 15 and the guide plate 17 a central guide plate 35 isarranged parallel to them, which can, with the aid of two pistoncylinders 36, whose piston rods 37 pass through the holes 38 in guideplate 15, be adjusted vertically, namely between a lower position, shownby a dot-dash line, which is limited by stops 39, and an upper position,shown by continuous lines. The central guide plate 35 has guide holes41, whose diameter D is larger than the diameter d of the adapter pins14. The amount of deviation a is defined in this case through the sizeof the guide holes 41. Through the moving of the central guide plate 35,the movement clearance space on all sides for the adapter pins 14 andthus the amount of deviation a can be altered, if the adapter pins 14are located above the guide plate 15. In the lower position of the plate35, the amount of deviation a is smaller than in the upper position.

If the same grid sizes are always present, it can also be advantageous,to arrange a central plate 35 rigidly about in the position portrayed inFIG. 4 in dot-dashed or continuous lines.

With the embodiment according to FIGS. 5 to 7, the adapter designatedhere by 45 has likewise a box construction. It comprises of a firstguide plate 46 with guide holes 47 at all grid points and with a secondguide plate 48 with guide holes 49 in the pattern of the testing pointsof the printed circuit board to be tested. The first guide plate 47 istransparent and consists, in a preferred embodiment, of plexiglass. Thesecond guide plate 48 does not need to be transparent and consists, in apreferred embodiment, of a synthetic material, strengthened with glassfibres, on an epoxy resin basis, which is designated in technicallanguage by EPG. In the fore plates 51 linking the guide plates 46, 48to one another, guides 52 in the form of guide slits are developed, inwhich the second guide plate 48 can be adjusted, for the purpose ofdistance alteration, between the guide plates 46, 48 vertically betweenan assembly position portrayed in FIG. 5 and a working positionportrayed in FIG. 7. The adjustment of the second guide plate 48 can beserved by a mechanism, which is portrayed by way of a suggestion in FIG.5 as a spindle drive 53 or a cylinder piston drive 54.

Of the present adapter pins four are designated by 55 to 58 anddescribed in particular further below.

FIG. 5 shows the guide plates 46, 48 and the adapter pins 55 to 58 in asection along the line V--V in FIG. 6, which shows a correspondingcutout of FIG. 5 in top view. The adapter pins 55 to 58 are, in theassembly position of the guide plate 48, pushed in from above throughthe guide holes designated by 59 to 62 in the first guide plate 46 andthe guide holes designated by 63 to 66 in the second guide plate 48. Ofthe guide holes in the second guide plate 48, that designated by 64 isdistant by a maximum distance d from the grid point allocated to it,namely the guide hole 60. The guide holes 63, 65 and 66 in the secondguide plate 48 (FIG. 6) have a smaller distance from the grid pointsallocated to them, namely guide holes 59, 61 and 62 in the first guideplate 46. The distance d amounts to half the diagonal extent e of a gridof four adjacent guide holes 47 in the first guide plate 46 arranged ina square, the size of such a grid being designated by R. The diameter fof the adapter pins, the diameter g of the guide holes 47 in the firstguide plate 46 and the thickness h of the first guide plate 46 arematched to one another, namely in such a way that the points 67 of theadapter pins 55 describe a gyrating circle 68, when an adapter pin, withits point 67 resting against the second guide plate 48, is moved in thesense of a gyrating movement, as is indicated for example by dot-dashedlines in FIG. 5. The above-described dimensions are matched to oneanother, so that the maximum radius of the gyrating circle 68corresponds to half the diagonal extent e and thus to the distance d.

The guide hole 64 in the second guide plate 48 has the peculiarity thatit lies on the diagonal i. As a result of this it has the same distanced from the guide holes designated by 59, 60 and 69, 70. That is, theadapter pin 56, which can still just be pushed in with some difficultythrough the guide hole 60 into the guide hole 64, by reason of thepreviously named dimensions, could also be introduced from any one ofthe guide holes 59 and 69 and 70, likewise still just with difficulty,into the guide hole 64. The assembly of such holes 64 in the secondguide plate 48, which lie in the intersection of diagonals i, which gothrough guide holes 59, 60, 69, 70, arranged in a square, is thusquadrupally indefinite. This difficulty is calculated for, in that theautomatic testing machine is in a position to learn the arrangement ofthe adapter pins which is present in the adapter, and to re-programeitself accordingly. The angle of deviation of the pin, which the adapterpins adopt compared with the perpendicular, is designated by k₁ in theassembly position according to FIG. 5, irrespective of its size. Throughthe moving of the second guide plate 48 into the working positionportrayed in FIG. 7, the angles of deviation of the pins diminish. Thediminished angles are designated in FIG. 7 by k₂. Hereby the smoothrunning of the adapter pins and certainly in particular of the adapterpins which are plugged into guide holes 64, which lie on theintersection of diagonals i, is guaranteed. A mutual contact of adapterpins 55 to 58 is avoided through the extending of the guide plates 46,48, because the adapter pins 55 to 58 thereby distance themselves fromone another.

For the above described embodiment the following dimension details aremade in addition:

thickness h of the first guide plate 46=1.5 mm

thickness l of the second guide plate 48=1.5 mm

diameter of the guide holes in the first and second guide plate 46,48=1.7 mm

separation m of the guide plates 46, 48 in the assembly position=3.5 mm,

diameter of the adapter pins=1.35 mm,

grid distance R of the guide holes 47 in the first guide plate=2.54 mm.

With the further embodiment according to FIG. 8, the adapter designatedhere by 75 has an upper first guide plate 76, a lower second guide plate77 and a third guide plate 78 arranged between them. As with thepreviously described embodiments, the guide plates 76 to 78 are arrangedparallel to one another. By contrast to the embodiment according to FIG.4, the third guide plate 78 is arranged rigidly here. It could certainlybe alterable in distance, however, only for the purpose of its basicpositioning. An alteration in distance at every assembly is not providedfor.

The adapter 75 of this embodiment is 100% reproducible. That means thatthe assembly of guide holes 79, in the second guide plate 77, lyingoutside the grid, may not be undefined. In other words, each guide hole79 in the second plate 77 is allocated for the assembly a quite definiteguide hole 80 in the first guide plate 76. The guide holes 80 in thefirst guide plate 76 are arranged in the grid. By contrast with theembodiment according to FIGS. 5 to 7, however, not at all grid points,but rather only at those which, for assembly of the special adapter 75,should receive adapter pins 81. The third guide plate 78 is providedwith guide holes 82, which can lie in and out of grid.

The guide holes 82, lying out of grid, in the third guide plate 78 are,however, compared with the nearest guide holes 80, located in the grid,of the first guide plate 76, displaced less far (v₁) than thecorresponding guide holes 79 in the second guide plate 77 (v₂). Thedisplacement v₁ of the guide holes 82 in the third guide plate 78 lyingout of grid is chosen so that--when the displacement v₁ is a maximumone--the in particular conical point 83 of the adapter pins 81 stilldips in every case into the guide holes 79 of the second guide plate 77,irrespective of the angle of deviation of the pin k₃ under which theadapter pins 81 are plugged-in in the first guide plate 76. Thedisplacement V₁ of the guide holes 82, located out of grid in the thirdguide plate 78, is determined in knowledge of the displacement v₂ of theguide holes 79, located out of grid, in the second guide plate 77, forexample calculated by a computer.

In comparable fashion as with the embodiment according to FIG. 5, alsowith the embodiment according to FIG. 8, the thickness h of the firstguide plate 76 and the movement clearance s of the adapter pins 81 inthe guide holes 80, as well as the movement clearance s, in the guideholes 82 of the third guide plate 78, are matched to one another so thatthe, if necessary pointed, points 83 of the adapter pins 81 dip into theguide holes 82 on plugging-in.

To the exemplary embodiment according to FIG. 8 the following dimensionvariables are given:

thickness of each of the three guide plates 76 to 78=1.7 mm

diameter of all guide holes 79, 80, 82=1.7 mm

diameter of the adapter pins 81=1.35 mm

the third guide plate 78 has a distance n to the second guide plate 77,which amounts to about 80% of the distance o between the first guideplate (76) and the second guide plate (77).

With all embodiments the adapter pins have a cylindrical shaft, aspherical head and a preferably conical point. The pin length l measuresmore than the transverse dimension p of the adapter by about the size ofthe spherical head.

FIG. 9 shows another adapter, which comprises a first guide plate 176, asecond guide plate 177 and a third guide plate 178 arranged in between.In the first guide plate 176 are holes 180 located in the grid. In thesecond guide plate 177 are the guide surface 179 likewise located in thegrid, as well as guide holes 179a located out of grid. The third guideplate 178 has guide holes 182 likewise located in the grid as well asguide holes 182a located out of grid. The displacement of the guideholes 182a, located out of grid, of the third guide plate compared withthe corresponding guide holes 180 in the first guide plate 176 is sochosen here that, with perpendicular introduction of an adapter pin 181into a guide hole 180 of the first guide plate 176, it is guaranteed, oneach, that the conical point of the adapter pin 181 still enters intothe corresponding guide hole 182a, located out of grid, of the thirdguide plate 178 and on the other hand--when the adapter pin 189 isguided further through the guide hole 182--this adapter pin 181 isinevitably led into the corresponding guide hole 179a located out ofgrid. In this fashion, in particular with the application of anautomatic loading system according to DE-OS No. 33 40 184, a practically100% efficiency with the loading within the shortest time is guaranteed.It is a significant feature of the invention that the adapter pins 181can be definitely introduced always perpendicularly into the guide holes180 of the first guide plate, namely irrespective of whether the guideholes in the second guide plate 177 are in the grid or out of grid.

The position of the guide holes 180 of the first guide plate 176 aregiven through the grid. The position of the guide holes 179, 179a in thesecond guide plate 177 is given through the hole picture of the printedcircuit board to be tested. The displacement of the guide holes 182a inthe third guide plate 178 can be calculated taking into account thepreviously named conditions and position data, whereto in particular acomputer is suitable. Thereto the plate diameter S, the pin diameter D,the hole diameter L, as well as the distances of the guide plated A₁, A₂and A₃ must be chosen so that the above mentioned desired condition canalways be realised, ie even when the displacement V₂ between a guidehole 180 in the first guide plate 176 and a guide hole 179a in thesecond guide plate 177, with regard to the reproducibility of an adapterloading diagram, is a maximum.

In FIG. 9, in particular with the left adapter pin 181, it can be seenthat half the diameter of the adapter pin D/2 is greater than thedisplacement V₁ between the guide hole 180 of the first guide plate 176and the guide hole 182a in the third guide plate 178. Thereby it isguaranteed that the adapter pin 181 still goes home with its point, onperpendicular introduction (designated in dashed lines), into thediameter region of the guide hole 182a of the third guide plate 178, isthen turned around and so continued that it finally goes home inevitablyinto the guide hole 179a of the second guide plate 177.

The method progression portrayed in FIG. 10 for indicating locations oferrors on a printed circuit board to be tested is as follows: by reasonof a pattern plate 190 corresponding to a printed circuit board to betested 198, a hole diagram is input into a computer 191. The datacorresponding to the hole diagram can be stored off on a data carrier,for example a diskette 192. It is equally possible to call the data backagain from the data carrier 192 and input the data into the computer191. The computer 191 now calculates the bore diagram for the holes ofthe guide plates of the adapter according to FIG. 9. The data orco-ordinates for this bore picture are input into an NC-boring machine193, by means of which the three guide plates 176, 177 and 178 arebored. After the boring the guide plates are assembled to the (stillunloaded) adapter 175. This is then put in an automatic loading device194 according to DE-OS No. 33 40 184. The adapter 175 loaded withadapter pins can be taken from the automatic loading device 194. Thisloaded adapter 175 is then supplied to a printed circuit board testingapparatus 197 together with the printed circuit board 198 to be tested.

The printed circuit board testing apparatus determines the data orco-ordinates of those testing contacts, which rest against the sphericalheads of the adapter pins. The testing contacts lie on the side of thefirst guide plate 176, that is all in the grid. Via the adapter pinsthese testing contacts stand connected to holes, affected by errors, ofthe printed circuit board 198 to be tested. The holes affected byerrors, of the printed circuit board 198 to be tested should beindicated. These, however, are partially out of grid, i.e. they lie onthe side of the second guide plate 177. In order now to determine thedata or co-ordinates of the holes, affected by errors, on the printedcircuit board to be tested, the data or co-ordinates, determined by theprinted circuit board testing apparatus 197, of the testing contactslocated in the grid are again supplied to the computer 191. The computerknows, by reason of the calculating data for the bore diagrams of thethree guide plates, the correlation between the data or co-ordinates ofthe testing points (holes), affected by errors, on the printed circuitboard to be tested on the one hand, and the data or co-ordinates of thetesting contacts of the printed circuit board testing apparatus 197 onthe other hand. The computer 191 transmits, correspondingly thereto, toan error indicating device 195 the data or co-ordinates of the testingpoints, affected by errors, of the printed circuit board 198 to betested, which correspond to the error co-ordinates or data of the holesin the second guide plate 177. These data or co-ordinates are indicatedon a monitor 196 and can be used by an operator, using an optical searchapparatus with co-ordinate indicator, to find the testing points,affected by errors on the printed circuit board 198 to be tested. It is,however, also possible to design the error indicating device 195 so thatit indicates testing points or holes, affected by errors, on the printedcircuit board 198 to be tested directly, for example by means of a lightpoint, which is produced by a projector head which can be moved in twoco-ordinate directions.

We claim:
 1. Adapter for a printed circuit board testing apparatus, bymeans of which testing contacts located in a grid can be connectedthrough adapter pins to testing points, located in and/or out of grid,of a printed circuit board to be tested, said adapter comprising firstand second guide plates arranged parallel to one another and at adistance from one another and having guide holes into which adapter pinscan be plugged, the guide holes in the first guide plate being arrangedin the grid and in the second guide plate in the pattern of the testingpoints of a printed circuit board to be tested, the first guide platehaving guide holes at all grid points, the distance between the firstand second guide plates being alterable between a working position, inwhich the guide plates have a separation shorter than the length of theadapter pins, and an assembly position, in which the guide plates have aseparation from one another which is reduced compared with the workingposition, and in that the separation in the assembly position is sochosen that an adapter pin to be introduced into a guide hole of thesecond guide plate can, as a result of a maximum angle of deviation ofthe pin defined by the pin diameter as well as the diameter and thelength of the guide holes of the first guide plate, be introducedthrough one of at most four guide holes, arranged next to one another ina square, of the first guide plate.
 2. Adapter according to claim 1wherein the first guide plate is transparent.
 3. Adapter according toclaim 1 wherein there is provided a guide between first and the secondguide plates for adjusting the first and/or the second guide plate. 4.Adapter according to claim 1 wherein there is provided an adjustingmechanism for adjusting the first and/or second guide plate.
 5. Adapterfor a printed circuit board testing apparatus, by means of which testingcontacts located in a grid on the testing apparatus can be connectedthrough adapter pins to testing points, located in and/or out of grid,of a printed circuit board to be tested, said adapter comprising first,second and third guide plates arranged parallel to one another and at adistance from one another, the third guide plate positioned between thefirst and the second guide plates, the guide plates having guide holes,into which adapter pins can be plugged-in, the first guide plate havingguide holes only at the grid locations to which testing contacts areallocated at the testing apparatus, the second and third guide plateshaving guide holes only at locations corresponding to the locations oftesting contacts at the printed circuit board, the guide holes lying outof grid, of the third guide plate, being displaced less far with respectto corresponding grid locations than the likewise corresponding guideholes lying out of grid, of the second guide plate in such a way thatthey lie in guide alignment between two guide holes allocated to oneanother, in the first and second guide plates.
 6. Adapter according toclaim 5, wherein the distance between the third guide plate and thesecond guide plate amounts to about 80% of the distance between thefirst guide plate and the second guide plate.
 7. Adapter according toclaim 5, wherein the lower guide plate is translucent.
 8. Adapteraccording to claim 7, wherein a mirror is arranged below the lower guideplate.
 9. Adapter according to claim 7 wherein a light source isarranged above the lower guide plate.
 10. Adapter according to claim 7,wherein a central guide plate is arranged parallel to and between thelower and the upper guide plates, the guide holes of the central guideplate being provided in all grid points and having a diameter whichallows a limited steering clearance of the adapter pins.
 11. Adapteraccording to claim 7, wherein at least one of the central guide plateand the upper guide plate is translucent.
 12. Adapter according to claim10 or 11, wherein the central guide plate is movable perpendicular tothe lower and upper guide plates.
 13. Adapter according to claim 1,wherein the adapter pins have spherical heads.
 14. Adapter according toclaim 9, wherein the light source is a hand lamp arranged above theupper guide plate.
 15. Adapter for a printed circuit board testingapparatus, by means of which testing contacts located in a grid can beconnected to testing points, located in and/or out of grid, of a printedcircuit board to be tested, through adapter pins, whose ends turnedtowards the testing points taper conically, with first and second guideplates and a third guide plate lying between the first and second guideplates, all three guide plates arranged parallel and at fixed distancesto one another and having guide holes for the adapter pins, the firstguide plate having guide holes located in the grid and the second guideplate guide holes located in and/or out of grid, which coincide with thetesting points of the printed circuit board to be tested, and the thirdguide plate having guide holes located in and/or out of grid, the guideholes located out of grid, of the third guide plate being placed sothat, the adapter pins with perpendicular introduction into the guideholes of the first guide plate, enter with their conically tapering endsinto the guide holes located out of grid of the third guide plate and,with further movement, are steered through these guide holes, locatedout of grid, of the third guide plate into the guide holes located outof grid, of the second guide plate.
 16. Adapter according to claim 15,wherein the distance between the first guide plate and the third guideplate is smaller than the distance between the third guide plate and thesecond guide plate.
 17. Adapter according to claim 15, wherein thedistance between the second guide plate and the third guide plateamounts to around 80% of the distance between the first guide plate andthe second guide plate.
 18. Adapter according to claim 15, wherein thethickness of the guide plates, the diameter of the guide holes, theseparations of the guide plates and the diameter of the adapter pins areso chosen that the adapter pins are properly positioned for all testingpoints, located out of grid, of a printed circuit board to be tested.19. Method for indicating the location of errors on a printed circuitboard to be tested, said printed circuit board having testing pointslocated in and/or out of grid, said method involving use of an adapterhaving first and second guide plates and a third guide platetherebetween, the first plate having holes lying in a grid and thesecond and third plates having holes located in and/or out of the gridand adapter pins which can extend through the holes and a printedcircuit board testing apparatus containing the adapter, to which theprinted circuit board to be tested is supplied, said method comprisingthe steps of supplying to a computer data of the co-ordinates of allcontact holes of the printed circuit board to be tested, causing thecomputer to calculate the co-ordinates of the bore holes for the threeguide plates, then boring the holes corresponding the calculatedco-ordinates into the three guide plates, thereafter assembling, fromthe three guide plates, the adapter and introducing the adapter pins tothe assembly, supplying the adapter, with the printed circuit board tobe tested, to the printed circuit board testing apparatus, thereupon,transmitting to the computer the data or co-ordinates, determined by theprinted circuit board testing apparatus, of those testing contactslocated in the testing apparatus grid, which correspond to printedcircuit board testing points affected by errors, causing the computer todetermine, by reason of these data or co-ordinates, the data orco-ordinates of the corresponding testing points of the printed circuitboard to be tested, and causing an indicating apparatus to indicate thelast mentioned data or co-ordinates.
 20. Adapter according to claim 2wherein there is provided a guide between the first and second guideplates for adjusting the first and/or second guide plate.
 21. Adapteraccording to claim 8 wherein a light source is arranged above the lowerguide plate.